Glass items are known to be formed using what are commonly known as I.S. forming machines, which comprise a number of side by side forming sections, each for producing a respective succession of glass items.
Each forming section comprises a rough mold, normally with a row of adjacent cavities, each for receiving a glass gob and forming a respective semifinished item. Each semifinished item is fed in a forming direction and transferred, by an inverter, to a finish mold, in which it is worked further to obtain the desired finish item, which is then extracted from the mold and unloaded.
The rough mold and finish mold each comprise two half-molds movable with respect to each other between a closed position and an open position.
The half-molds are moved between the open and closed positions by a mold opening/closing group, which comprises, for each mold, two actuating arms connected to respective half-molds and which are hinged to a fixed structure and rotated in opposite directions about vertical axes by a mechanical crank transmission. The transmission is activated by a linear actuator, the translating output member of which is movable both ways in a direction perpendicular to the fixed vertical hinge axes.
Though widely used in conventional forming sections, known mold opening/closing groups of the above type are practically uninstallable in last-generation forming sections, mainly on account of their bulk in the forming direction. This is mainly due to the type of transmissions employed, and to the location of the actuator, which must be located as close as possible to the molds to minimize the slack inevitably present in the linkages connecting the actuator to the arms.
The bulk of the opening/closing group in the forming direction also poses various problems when removing the group from the section, e.g. for routine servicing or in the event of a malfunction, on account of removal also involving removal of other component parts of the section.
Moreover, in known transmissions, if one of the linkages connecting the actuator to the relative arm should for any reason be overloaded with respect to the other, consistent positioning of the half-molds, especially in the closed position, is no longer assured, thus impairing the quality of the finished items.